318 Mr. J. W. Fewkes on a new Physophore. 



The most exceptional peculiarity in the genus is the struc- 

 ture of an organ called the hood, elsewhere unknown among 

 Physophores in this form, although represented by organs 

 which have ah-eady been described in other little-known 

 genera. This homology of these structures, however, is here 

 pointed out for the first time. A diagnosis of the genus 

 Ploeophysa, of which only the single species P. Agassizii is 

 known, is given in the following pages. The account closes 

 with a discussion of its affinities and its relationships to 

 certain other Physophores. 



I. Description o/'Ploeophysa Agassizii, gen. et sp. nov. 



Plcbophysa, gen. nov. 



Float large, conspicuous, partially covered by a hood- 

 shaped body, which is (or appears to be) bound by muscular 

 bands to a globular enlargement of the polyp-stem. 



No nectocalyces, no hydrophyllia. Polyp-stem globular, 

 bearing numerous, long, flexible tasters, without (?) fila- 

 ments. Polypites situated below the crown of tasters. 

 Polygastric. Tentacles with tentacular knobs formed of a 

 sacculus, two terminal filaments, and a terminal vesicle. 

 Rudimentary involucrum at the base of the sacculus. Sexual 

 clusters in botryoidal bunches at the base of the tasters. 

 Monoecious. 



Diameter of the float in a horizontal direction 5 millim. 

 Whole diameter with contracted tasters (hydrocysts) 12-15 

 millim. Colourless* in alcohol, with the exception of the 

 pigment- zone about the apex of the float. 



Ploeophysa Agassizii, sp. nov. (PI. XVII.) 



Float. — The float [f) is large and hemispherical, with a 

 pigment-zone at the apex, as in AtJwryhia. The lower hemi- 

 sphere of the float is inflated and passes directly into a globu- 

 lar enlargement of the polyp-stem known as the polyp-sac. 

 Size 2 millim. in horizontal diameter. 



Hood. — On one side of the float there rises a structure 

 called the hood [li). This organ arches over the float in 

 alcoholic specimens and appears to be a continuation of the 

 polyp- sac. Its outer walls are papillose, and the whole struc- 

 ture appears to be glandular. It is connected with the polyp- 



* A universal cliaracterisiic of all specimens of Physophores which 

 have been in alcohol for a length of time. 



